It is already known that by rapidly supplying gas a bag can be inflated at the moment of a collision and form a gas-filled buffer which thus acts as a shock-absorbing protection means. Since, expecially in the case of front-seat passengers, the bags or shells must be extremely large when inflated and the time for inflation must be extremely short, typically a few hundredths of a second, extremely high gas speeds are required to effect this inflation. This has in turn caused considerable problems due, amongst other things to the loud noise occuring as a result of the rapid inflation. In addition, the over-pressure occuring in a closed car, for example, when one or more of these protection means is rapidly inflated may damage the hearing mechanism of the passengers and even cause permanent injury.